$OpenBSD: patch-src_bootstrap_lib_rs,v 1.3 2017/05/05 11:40:29 landry Exp $
Let us compilation choice to be honored.
--- src/bootstrap/lib.rs.orig	Mon Apr 24 20:53:45 2017
+++ src/bootstrap/lib.rs	Wed Apr 26 08:43:00 2017
@@ -848,7 +848,6 @@ impl Build {
         // gcc-rs because the build scripts will determine that for themselves.
         let mut base = self.cc[target].0.args().iter()
                            .map(|s| s.to_string_lossy().into_owned())
-                           .filter(|s| !s.starts_with("-O") && !s.starts_with("/O"))
                            .collect::<Vec<_>>();
 
         // If we're compiling on OSX then we add a few unconditional flags
